Fix warnings from upgrading to ghc 8.8.3

src/Polysemy/Embed.hs

@@ -12,7 +12,6 @@ module Polysemy.Embed
   ) where
 
 import Polysemy
-import Polysemy.Embed.Type (Embed (..))
 
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 -- | Given a natural transform from @m1@ to @m2@

src/Polysemy/Internal.hs

@@ -40,7 +40,6 @@ module Polysemy.Internal
 
 import Control.Applicative
 import Control.Monad
-import Control.Monad.Fail
 import Control.Monad.Fix
 import Control.Monad.IO.Class
 import Data.Functor.Identity

src/Polysemy/Internal/Union.hs

@@ -265,14 +265,13 @@ decomp (Union p a) =
 -- | Retrieve the last effect in a 'Union'.
 extract :: Union '[e] m a -> Weaving e m a
 extract (Union Here a)   = a
-extract (Union (There g) _) = case g of {}
 {-# INLINE extract #-}
 
 
 ------------------------------------------------------------------------------
 -- | An empty union contains nothing, so this function is uncallable.
 absurdU :: Union '[] m a -> b
-absurdU (Union pr _) = case pr of {}
+absurdU = \case {}
 
 
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